I know of two types; I call them a ring loader and a strap loader. These may not be the "technical" names. The ring loader is by far the more popular. The Sten mag is next to impossible to load by hand. I will try to search for a picture for you. Here is a link where you can order Sten mag loaders.

I've got both of those and find the Ohio Ord one to be much, much better. (but it costs more) There is also a "spoon" type and a Belgian type for Vignon (sp?) SMG or maybe Lanchester. (I think I.M.A. sells it)